1. Field of the Invention
The invention relates to a filter cigarette with a nicotine-to-condensate-ratio of 1.3 at the maximum comprising a tobacco rod surrounded by a cigarette paper, a first filter element facing the tobacco rod and consisting of a fibrous material having a low single denier, a high total denier and an appropriately high retention capacity, a second filter element facing the mouth of the smoker and having a low retention capacity, a hollow chamber disposed between the two filter elements and having a length of 3 to 7 mm at an overall length of the filter between 18 and 30 mm, an air-impermeable tipping paper for attaching the two filter elements to the tobacco rod and a filter ventilation zone in the tipping paper in the region of the hollow chamber, said filter ventilation zone extending in the circumferential direction and being produced on the finished filter cigarette by mechanical means or by laser irradiation.
2. Description of the Prior Art
Such a filter cigarette is known from the embodiment shown in FIG. 3 of published European patent application No. 101,173, and comprises a tobacco rod surrounded by a cigarette paper, a first filter element facing the tobacco rod made of a fibrous material with a low single denier and a high total denier and having an appropriately high retention capacity, a second filter element facing the mouth of the smoker and having a low retention capacity, a hollow chamber disposed between the two filter elements and having a length of 3 to 7 mm at an overall filter length between 18 mm and 30 mm, a wrapper surrounding the two filter elements and the hollow chamber, an air-impermeable tipping paper for attaching the two filter elements to the tobacco rod, and a filter ventilation zone (in the tipping paper and the wrapper) extending in circumferential direction located in the region of the hollow chamber and made on the finished filter cigarette mechanically or by laser beams.
No detailed information is given regarding the dimensions and/or properties of the various elements of this filter and of the tobacco rod other than pointing out that the filter element facing the tobacco rod effects the predominant portion of the filter efficiency, namely in the range of 80 to 90% or more, and therefore consists of a Tow Material with a small single denier and large total denier, while the filter efficiency of the filter element facing the mouth of the smoker is relatively small.
Here, the ventilation air passes through the ventilation zone into the hollow chamber and is mixed thereat with the smoke stream which has already been strongly filtered through the filter element facing the tobacco rod. This mixture then flows through the second filter element facing the mouth of the smoker and having only a relatively low filter efficiency, and reaches the mouth of the smoker from there.
This structure is supposed to provide improved taste due to the fact that the major portion of the components of the smoke affecting the taste reaches the mouth of the smoker, while the nicotine-to-condensate-ratio is relatively high.
Such a filter cigarette provides a significantly more intense taste sensation than filter cigarettes which are equal in accordance with DIN standards, i.e. with respect to condensate and nicotine, and have a ventilated cellulose acetate single filter or ventilated double filters without a mixing chamber. Furthermore due to the blending and/or thorough mixing of smoke and ventilation air in the hollow or mixing chamber, no typical smoke pattern arises at the mouth side of the second filter element. Smoker tests have shown that such patterns are undesirable; with conventionally ventilated filters, "white ring" is formed by the ventilation air enveloping the smoke; other patterns can be formed if air and smoke are conducted separately to the exit end of the filter facing the mouth of the smoker, as well as "star-shaped" patterns for ventilation through few but very large perforation holes. Other smoke patterns have also been observed and objected to.
A nicotine-to-condensate-ratio of 1.5 can be obtained with these filter cigarettes of known construction, this ratio being computed from the formula: EQU nicotine content/condensate.times.10.
For many applications, however, an attempt is made to obtain smaller nicotine-to-condensate-ratios of 1.3 at the maximum. Furthermore, smoker tests have shown that for many variants of such a filter consisting of three filter elements, the taste sensation still leaves something to be desired.